This invention relates to surface effect ship constructions, wherein aluminum alloy materials are largely used throughout the vessel hull and specifically are employed to construct the outside hull and hull bottom platings. Such vessels typically employ water propeller propulsion systems which are carried beneath the side hulls of the vessel by means of struts extending downwardly therefrom in laterally canted cantilever fashion. The cantilever base arrangement in this case is therefore called upon to combat a variety of omni-directionally related forces such as are imposed on the strut such as by cyclically imposed propeller operation vibrations; as well as forces imposed on the strut incidental to ship heave/roll and forward/reverse speed acceleration maneuverings of the ship and propeller groundings.
In order to provide the propeller support strut to be of minimum cross-sectional thickness (so as to minimize high speed operating drag effects) and to be of sufficient strength, such struts are required to be fabricated of high strength steel. The underwater junctures of such steel struts and aluminum alloy hull structures have therefore been vulnerable to dissimilar metal electrolytic corrosion effects with the result that the operational stresses thereon soon result in serious problems such as fatigue cracking of the supporting aluminum alloy based structure.
It is the object of the present invention to provide in an aluminum alloy hulled ship as aforesaid improvement in the method and means for mounting in cantilever extended relation below an aluminum alloy keel plate thereof a superior strength thin-profile steel strut, for operationally supporting the drive shaft of a ship propeller while avoiding the above referred to problems.